The field of the invention pertains to measuring devices, in particular to protractors for measuring angles. Such protractors are used for measuring angles over small distances on drawing boards and sketches or plans, however, when angles need to be measured over long distances a simple hand held plastic device is not adequate.
Typically, measurement of angles over long distances has required the use of a surveyor""s transit, however, a surveyor""s transit is a bulky device mounted on a tripod and designed for use over relatively great distances such as for the measurement of land parcels. In recent years, laser sending and receiving devices in combination with dedicated computing electronics and global positioning systems (GPS) have been added to transits to provide significantly more accurate results. These improvements to transits, while very useful, have added considerable cost to the transits because the improvements must be protected against the hazards of outdoor use in inclement weather.
Intermediate distances are encountered in building construction. The distances are too great for small protractors but do not require the accuracy of laser transits. Ordinary transits continue to be used in building construction. More recently construction levels have been fitted with laser pointers to extend their xe2x80x9creachxe2x80x9d both vertically and horizontally. Other devices have been developed to align holes vertically for plumbing installation. However, there remains a need for a more universally useful device to measure angles at intermediate distances such as for short sewer lines, roof pitches, drain fields, drainage ditches, foundation footings and landscaping.
As a result of the development of relatively inexpensive laser pointers, a truly useful laser protractor is a realistic goal. Disclosed below is a laser protractor comprising two laser pointers fixed in a body to point at exactly 90xc2x0 apart in a plane formed by the laser pointers. A third laser pointer is mounted on a movable arm rotatable about an axis perpendicular to the intersection of the first two laser pointers (as extended). With suitable leveling bubbles and degree scales on the body an intermediate distance laser protractor is created by the combination. The laser protractor, because of its simple rugged construction can be made inexpensively with simple off the shelf laser pointers, each battery powered with inexpensive batteries.